Ganglioside Composition Research Articles

Glycosphingolipids in Osteoarthritis and Cartilage-Regeneration Therapy: Mechanisms and Therapeutic Prospects Based on a Narrative Review of the Literature.

Glycosphingolipids (GSLs), a subtype of glycolipids containing sphingosine, are critical components of vertebrate plasma membranes, playing a pivotal role in cellular signaling and interactions. In human articular cartilage in osteoarthritis (OA), GSL expression is known notably to decrease. This review focuses on the roles of gangliosides, a specific type of GSL, in cartilage degeneration and regeneration, emphasizing their regulatory function in signal transduction. The expression of gangliosides, whether endogenous or augmented exogenously, is regulated at the enzymatic level, targeting specific glycosyltransferases. This regulation has significant implications for the composition of cell-surface gangliosides and their impact on signal transduction in chondrocytes and progenitor cells. Different levels of ganglioside expression can influence signaling pathways in various ways, potentially affecting cell properties, including malignancy. Moreover, gene manipulations against gangliosides have been shown to regulate cartilage metabolisms and chondrocyte differentiation in vivo and in vitro. This review highlights the potential of targeting gangliosides in the development of therapeutic strategies for osteoarthritis and cartilage injury and addresses promising directions for future research and treatment.

Defining the Ceramide Composition of Bovine and Human Milk Gangliosides by Direct Infusion ESI-CID Tandem Mass Spectrometry of Native and Permethylated Molecular Species.

Gangliosides are glycosphingolipids composed of an oligosaccharide that contains one or more sialic acid residues and is linked to a ceramide, a lipid composed of a long chain base (LCB) that bears an amide-linked fatty acyl group (FA). The ceramide portions of gangliosides are embedded in cell membranes; the exposed glycans interact with the extracellular environment. Gangliosides play a myriad of roles in activities such as cell-cell communication, formation of lipid rafts, cellular adhesion, calcium homeostasis, host-pathogen interaction, and viral invasion. Although the epitopes responsible for the interactions of gangliosides are located in the glycan, the epitope presentation is strongly influenced by the orientation of the attached ceramide within the lipid membrane, a feature that depends on the details of its structure, that is, the specific LCB and FA. Since the identities of both the glycan and the ceramide affect the activity of gangliosides, it is important to characterize the individual intact molecular forms. We report here a mass spectrometry-based method that combines the information gained from low-energy collision-induced dissociation (CID) measurements for the determination of the glycan with tandem mass spectra obtained at stepped higher-energy CID for the detailed characterization of the LCB and FA components of intact gangliosides. We provide results from applications of this method to the analysis of gangliosides present in bovine and human milk in order to demonstrate the assignment of LCB and FA for intact gangliosides and differential detection of isomeric ceramide structures.

Kinetics of Ganglioside-Rich Supported Lipid Bilayer Formation with Tracer Vesicle Fluorescence Imaging.

Gangliosides, forming a class of lipids complemented by sugar chains, influence the lateral distribution of membrane proteins or membrane-binding proteins, act as receptors for viruses and bacterial toxins, and mediate several types of cellular signaling. Gangliosides incorporated into supported lipid bilayers (SLBs) have been widely applied as a model system to examine these biological processes. In this work, we explored how ganglioside composition affects the kinetics of SLB formation using the vesicle rupturing method on a solid surface. We imaged the attachment of vesicles and the subsequent SLB formation using the time-lapse total internal reflection fluorescence microscopy technique. In the early phase, the ganglioside type and concentration influence the adsorption kinetics of vesicles and their residence/lifetime on the surface before rupturing. Our data confirm that a simultaneous rupturing of neighboring surface-adsorbed vesicles forms microscopic lipid patches on the surface and it is triggered by a critical coverage of the vesicles independent of their composition. In the SLB growth phase, lipid patches merge, forming a continuous SLB. The propagation of patch edges catalyzes the process and depends on the ganglioside type. Our pH-dependent experiments confirm that the polar/charged head groups of the gangliosides have a critical role in these steps and phases of SLB formation kinetics.

Impact of dietary n-3 polyunsaturated fatty acid intake during the perinatal and post-weaning periods on the phospholipid and ganglioside composition of olfactory tissues.

The olfactory mucosa (OM) and olfactory bulb (OB) are neuronal tissues that contribute to the early processing of olfactory information. They contain significant amounts of n-3 and n-6 polyunsaturated fatty acids (PUFAs), which are crucial for neuronal tissue development. In this study, we evaluated the impact of feeding mice diets that are either deficient in α-linolenic acid (ALA) or supplemented with n-3 long-chain PUFAs from gestation to adolescence on the phospholipid and ganglioside composition of these tissues. Both diets modified the levels of some phospholipid classes, notably the phosphatidylserine and phosphatidylethanolamine levels. In addition, the low-ALA diet enriched n-6 PUFAs in the main phospholipid classes of both tissues, while the diet supplemented with n-3 PUFAs enhanced the n-3 PUFA-containing phospholipid species level, mainly in OM. The diets also modulated the levels and profiles of several ganglioside classes in OM and OB. These modifications may have repercussions on the olfactory sensitivity.

HIPPOCAMPAL GANGLIOSIDE COMPOSITION IS ALTERED BY METFORMIN AND LIRAGLUTIDE TREATMENT IN A HIGH-FAT HIGH-SUGAR DIET RAT MODEL.

Insulin resistance has many deleterious effects on the central nervous system, including the initiation and potentiation of neurodegeneration. While the pathogenesis of Alzheimer's disease has been extensively researched with many insights into the effects of amyloids and neurofibrillary tangles, the connection between the two pathogenic entities has not yet been fully elucidated. Gangliosides are commonly found in neuronal membranes and myelin, specifically in lipid rafts that have been linked to pathological amyloidogenesis. In this study, 64 Sprague Dawley rats with equal sex distribution were separated into four sex-specific groups, as follows: control group on standard diet; group on high-fat, high-sugar diet (HFHSD); group on HFHSD treated with metformin; and group on HFHSD treated with liraglutide. Free-floating immunohistochemistry of the rat hippocampi was performed to analyze group-specific and sex-specific changes in the composition of the four most common gangliosides found in neuronal membranes and myelin sheaths, GM1, GD1a, GD1b and GT1b. The groups on HFHSD showed glucose tolerance impairment and body weight increase at the end of the experiment, whereas the groups treated with pharmacotherapeutics had better insulin sensitivity and decreases in body weight by the end of the experiment. Most changes were observed for GM1 and GD1b. Positive immunoreactivity for GM1 was observed in the male group treated with liraglutide in regions where it is not physiologically found. The changes observed following HFHSD and liraglutide treatment were suggestive of ganglioside restructuring that might have implications on pathological amyloidogenesis. Metformin treatment did not significantly alter the hippocampal ganglioside composition in either sex.

Liver-Secreted Hexosaminidase A Regulates Insulin-Like Growth Factor Signaling and Glucose Transport in Skeletal Muscle.

Nonalcoholic fatty liver disease (NAFLD) and impaired glycemic control are closely linked; however, the pathophysiological mechanisms underpinning this bidirectional relationship remain unresolved. The high secretory capacity of the liver and impairments in protein secretion in NAFLD suggest that endocrine changes in the liver are likely to contribute to glycemic defects. We identify hexosaminidase A (HEXA) as an NAFLD-induced hepatokine in both mice and humans. HEXA regulates sphingolipid metabolism, converting GM2 to GM3 gangliosides-sphingolipids that are primarily localized to cell-surface lipid rafts. Using recombinant murine HEXA protein, an enzymatically inactive HEXA(R178H) mutant, or adeno-associated virus vectors to induce hepatocyte-specific overexpression of HEXA, we show that HEXA improves blood glucose control by increasing skeletal muscle glucose uptake in mouse models of insulin resistance and type 2 diabetes, with these effects being dependent on HEXA's enzymatic action. Mechanistically, HEXA remodels muscle lipid raft ganglioside composition, thereby increasing IGF-1 signaling and GLUT4 localization to the cell surface. Disrupting lipid rafts reverses these HEXA-mediated effects. In this study, we identify a pathway for intertissue communication between liver and skeletal muscle in the regulation of systemic glycemic control.

Interorgan Metabolism of Ganglioside Is Altered in Type 2 Diabetes.

GM3 is implicated in cell signaling, inflammation and insulin resistance. The intestinal mucosa metabolizes ganglioside and provides gangliosides for uptake by peripheral tissues. Gangliosides downregulate acute and chronic inflammatory signals. It is likely that transport of intestinal derived gangliosides to other tissues impact the same signals characteristic of inflammatory change in other chronic conditions such as Type 2 Diabetes (T2DM). The postprandial ceramide composition of GM3 and other gangliosides in plasma and chylomicrons has not been examined in T2DM. The present study assessed if diet or T2DM alters ganglioside components in plasma and chylomicrons secreted from the intestinal mucosa after a meal. GD1, GD3, and GM3 content of chylomicrons and plasma was determined by LC/triple quad MS in non-diabetic (control) and T2DM individuals in the fasting and postprandial state after 2 days of consuming a low or high fat diet in a randomized blinded crossover design. Diet fat level did not alter baseline plasma or chylomicron ganglioside levels. Four hours after the test meal, plasma monounsaturated GD3 was 75% higher, plasma saturated GD3 was 140% higher and plasma polyunsaturated GM3 30% lower in diabetic subjects compared to control subjects. At 4 h, chylomicron GD1 was 50% lower in T2DM compared to controls. The proportion of d34:1 in GD3 was more abundant and d36:1 in GD1 less abundant in T2DM compared to control subjects at 4 h. The present study indicates that T2DM alters ceramide composition of ganglioside available for uptake by peripheral tissues.

Ganglioside lipidomics of CNS myelination using direct infusion shotgun mass spectrometry

SummaryGangliosides are present and concentrated in axons and implicated in axon-myelin interactions, but how ganglioside composition changes during myelin formation is not known. Here, we present a direct infusion (shotgun) lipidomics method to analyze gangliosides in small amounts of tissue reproducibly and with high sensitivity. We resolve the mouse ganglioside lipidome during development and adulthood and determine the ganglioside content of mice lacking the St3gal5 and B4galnt1 genes that synthesize most ganglioside species. Our results reveal substantial changes in the ganglioside lipidome during the formation of myelinated nerve fibers. In sum, we provide insights into the CNS ganglioside lipidome with a quantitative and sensitive mass spectrometry method. Since this method is compatible with global lipidomic profiling, it will provide insights into ganglioside function in physiology and pathology.

Start Me Up: How Can Surrounding Gangliosides Affect Sodium-Potassium ATPase Activity and Steer towards Pathological Ion Imbalance in Neurons?

Gangliosides, amphiphilic glycosphingolipids, tend to associate laterally with other membrane constituents and undergo extensive interactions with membrane proteins in cis or trans configurations. Studies of human diseases resulting from mutations in the ganglioside biosynthesis pathway and research on transgenic mice with the same mutations implicate gangliosides in the pathogenesis of epilepsy. Gangliosides are reported to affect the activity of the Na+/K+-ATPase, the ubiquitously expressed plasma membrane pump responsible for the stabilization of the resting membrane potential by hyperpolarization, firing up the action potential and ion homeostasis. Impaired Na+/K+-ATPase activity has also been hypothesized to cause seizures by several mechanisms. In this review we present different epileptic phenotypes that are caused by impaired activity of Na+/K+-ATPase or changed membrane ganglioside composition. We further discuss how gangliosides may influence Na+/K+-ATPase activity by acting as lipid sorting machinery providing the optimal stage for Na+/K+-ATPase function. By establishing a distinct lipid environment, together with other membrane lipids, gangliosides possibly modulate Na+/K+-ATPase activity and aid in “starting up” and “turning off” this vital pump. Therefore, structural changes of neuronal membranes caused by altered ganglioside composition can be a contributing factor leading to aberrant Na+/K+-ATPase activity and ion imbalance priming neurons for pathological firing.

A Lack of GD3 Synthase Leads to Impaired Renal Expression of Connexins and Pannexin1 in St8sia1 Knockout Mice.

The aim of this study was to determine the effects of altered ganglioside composition on the expression of Cx37, Cx40, Cx43, Cx45, and Panx1 in different kidney regions of St8sia1 gene knockout mice (St8sia1 KO) lacking the GD3 synthase enzyme. Experiments were performed in twelve male 6-month-old mice: four wild-type (C57BL/6-type, WT) and eight St8sia1 KO mice. After euthanasia, kidney tissue was harvested, embedded in paraffin wax, and processed for immunohistochemistry. The expression of connexins and Panx1 was determined in different regions of the kidney: cortex (CTX.), outer stripe of outer medulla (O.S.), inner stripe of outer medulla (IN.S.), and inner medulla (IN.MED.). We determined significantly lower expression of Cx37, Cx40, Cx45, and Panx1 in different parts of the kidneys of St8sia1 KO mice compared with WT. The most consistent decrease was found in the O.S. where all markers (Cx 37, 40, 45 and Panx1) were disrupted in St8si1 KO mice. In the CTX. region, we observed decrease in the expression of Cx37, Cx45, and Panx1, while reduced expression of Cx37 and Panx1 was more specific to IN.S. The results of the present study suggest that deficiency of GD3 synthase in St8sia1 KO mice leads to disruption of renal Cx expression, which is probably related to alteration of ganglioside composition.

Gangliosides as Biomarkers of Human Brain Diseases: Trends in Discovery and Characterization by High-Performance Mass Spectrometry.

Gangliosides are effective biochemical markers of brain pathologies, being also in the focus of research as potential therapeutic targets. Accurate brain ganglioside mapping is an essential requirement for correlating the specificity of their composition with a certain pathological state and establishing a well-defined set of biomarkers. Among all bioanalytical methods conceived for this purpose, mass spectrometry (MS) has developed into one of the most valuable, due to the wealth and consistency of structural information provided. In this context, the present article reviews the achievements of MS in discovery and structural analysis of gangliosides associated with severe brain pathologies. The first part is dedicated to the contributions of MS in the assessment of ganglioside composition and role in the specific neurodegenerative disorders: Alzheimer’s and Parkinson’s diseases. A large subsequent section is devoted to cephalic disorders (CD), with an emphasis on the MS of gangliosides in anencephaly, the most common and severe disease in the CD spectrum. The last part is focused on the major accomplishments of MS-based methods in the discovery of ganglioside species, which are associated with primary and secondary brain tumors and may either facilitate an early diagnosis or represent target molecules for immunotherapy oriented against brain cancers.

An iPSC model of hereditary sensory neuropathy-1 reveals L-serine-responsive deficits in neuronal ganglioside composition and axoglial interactions

SummaryHereditary sensory neuropathy type 1 (HSN1) is caused by mutations in the SPTLC1 or SPTLC2 sub-units of the enzyme serine palmitoyltransferase, resulting in the production of toxic 1-deoxysphingolipid bases (DSBs). We used induced pluripotent stem cells (iPSCs) from patients with HSN1 to determine whether endogenous DSBs are neurotoxic, patho-mechanisms of toxicity and response to therapy. HSN1 iPSC-derived sensory neurons (iPSCdSNs) endogenously produce neurotoxic DSBs. Complex gangliosides, which are essential for membrane micro-domains and signaling, are reduced, and neurotrophin signaling is impaired, resulting in reduced neurite outgrowth. In HSN1 myelinating cocultures, we find a major disruption of nodal complex proteins after 8 weeks, which leads to complete myelin breakdown after 6 months. HSN1 iPSC models have, therefore, revealed that SPTLC1 mutation alters lipid metabolism, impairs the formation of complex gangliosides, and reduces axon and myelin stability. Many of these changes are prevented by l-serine supplementation, supporting its use as a rational therapy.

Gangliosides as Signaling Regulators in Cancer.

At the plasma membrane, gangliosides, a group of glycosphingolipids, are expressed along with glycosphingolipids, phospholipids, and cholesterol in so-called lipid rafts that interact with signaling receptors and related molecules. Most cancers present abnormalities in the intracellular signal transduction system involved in tumor growth, invasion, and metastasis. To date, the roles of gangliosides as regulators of signal transduction have been reported in several cancer types. Gangliosides can be expressed by the exogenous ganglioside addition, with their endogenous expression regulated at the enzymatic level by targeting specific glycosyltransferases. Accordingly, the relationship between changes in the composition of cell surface gangliosides and signal transduction has been investigated by controlling ganglioside expression. In cancer cells, several types of signaling molecules are positively or negatively regulated by ganglioside expression levels, promoting malignant properties. Moreover, antibodies against gangliosides have been shown to possess cytotoxic effects on ganglioside-expressing cancer cells. In the present review, we highlight the involvement of gangliosides in the regulation of cancer cell signaling, and we explore possible therapies targeting ganglioside-expressing cancer.

Very long-chain acyl-CoA synthetase 3 mediates onco-sphingolipid metabolism in malignant glioma.

Gliomas are the largest category of primary malignant brain tumors in adults, and glioblastomas account for nearly half of malignant gliomas. Glioblastomas are notoriously aggressive and drug-resistant, with a very poor 5 year survival rate of about 5%. New approaches to treatment are thus urgently needed. We previously identified an enzyme of fatty acid metabolism, very long-chain acyl-CoA synthetase 3 (ACSVL3), as a potential therapeutic target in glioblastoma. Using the glioblastoma cell line U87MG, we created a cell line with genomic deletion of ACSVL3 (U87-KO) and investigated potential mechanisms to explain how this enzyme supports the malignant properties of glioblastoma cells. Compared to U87MG cells, U87-KO cells grew slower and assumed a more normal morphology. They produced fewer, and far smaller, subcutaneous xenografts in nude mice. Acyl-CoA synthetases, including ACSVL3, convert fatty acids to their acyl-CoA derivatives, allowing participation in diverse downstream lipid pathways. We examined the effect of ACSVL3 depletion on several such pathways. Fatty acid degradation for energy production was not affected in U87-KO cells. Fatty acid synthesis, and incorporation of de novo synthesized fatty acids into membrane phospholipids needed for rapid tumor cell growth, was not significantly affected by lack of ACSVL3. In contrast, U87-KO cells exhibited evidence of altered sphingolipid metabolism. Levels of ceramides containing 18-22 carbon fatty acids were significantly lower in U87-KO cells. This paralleled the fatty acid substrate specificity profile of ACSVL3. The rate of incorporation of stearate, an 18-carbon saturated fatty acid, into ceramides was reduced in U87-KO cells, and proteomics revealed lower abundance of ceramide synthesis pathway enzymes. Sphingolipids, including gangliosides, are functional constituents of lipid rafts, membrane microdomains thought to be organizing centers for receptor-mediated signaling. Both raft morphology and ganglioside composition were altered by deficiency of ACSVL3. Finally, levels of sphingosine-1-phosphate, a sphingolipid signaling molecule, were reduced in U87-KO cells. We conclude that ACSVL3 supports the malignant behavior of U87MG cells, at least in part, by altering cellular sphingolipid metabolism.

High resolution mass spectrometry provides novel insights into the ganglioside pattern of brain cavernous hemangioma

In this study we have optimized nanoelectrospray ionization (nanoESI) high resolution mass spectrometry (HR MS) performed on Orbitrap instrument in the negative ion mode for the determination of the composition and structure of gangliosides extracted from human brain cavernous hemangioma.The optimized HR MS platform, allowed the discrimination of 62 ions, corresponding to 52 different ganglioside species, which represents roughly twice the number of species existing in the current inventory of human brain hemangioma-associated gangliosides. The experiments revealed a ganglioside pattern dominated by GD-type of structures as well as an elevated incidence of species characterized by a low degree of sialylation and short glycan chains, including asialo GA1 (d18:1/18:0), which offer a new perspective upon the ganglioside composition in this benign tumor. Many of the structures are characteristic for this type of tumor only and are to be considered in further investigations for their potential use in early brain hemangioma diagnosis based on molecular markers. The detailed fragmentation analysis performed by collision-induced dissociation (CID) tandem MS provided information of structural elements related to the glycan core and ceramide moiety, which confirmed the molecular configuration of GD3 (d18:1/24:1) and GD3 (d18:1/24:2) species with potential biomarker role.

Abstract 4525: Dynamic changes in patterns of ganglioside expression characterize maturation of cytotoxic T cells and natural killer cells into effector cells and suggest a close relationship between the two cell types

Abstract Gangliosides are glycosphingolipids that play important regulatory roles in cell signaling. Their patterns of expression during human lymphoid cell development and differentiation, however are not not known. Here, we used the ganglioside-binding B subunits of E. coli enterotoxins (LT-IIa-B, LT-IIb-B and LT-IIc-B) as molecular probes to dissect the membrane ganglioside composition of human CD8+ T cells and NK cells, two important players in the anti-tumor response. Human normal PBMC isolated from leukoreduction filters by Ficoll density gradient centrifugation were stained with recombinant LT-IIa-B, LT-IIb-B or LT-IIc-B, and with monoclonal antibodies to CD3, CD8, CD16, CD19, CD27, CD62L, CD45RA, CD45RO and CD56. Using FACS analysis, we found that ganglioside ligands for LT-IIb-B (avidity: GD1a>GT1b>GM2/GM3) and LT-IIc-B (avidity: GM1>GM2 >GM3/GD1a) were increasingly expressed during transitions from naïve T cells, either (CD8+CD45RA+CD62L+) or (CD8+CD45RO-CD27+), to memory T cells of both central memory (CD8+CD45RA-CD62L+) and effector memory (CD8+CD45RA-CD62L-) phenotypes and from memory T cells (CD8+CD45RO+CD27+) to terminally differentiated effector memory (CD8+CD45RO+CD27-) T cells, with expression of ganglioside ligands for LT-IIb-B exhibiting the most significant increase. Patterns of ganglioside expression in the NK cell subsets were remarkably similar to those observed in the CD8+ T cell subsets: Ganglioside ligands for LT-IIb-B and LT-IIc-B were increasingly expressed during transitions from circulating naïve (CD16dimCD56bright) to effector (CD16+CD56dim) NK cells and from effector NK cells to activated mature (CD16+CD56-) NK cells, with expression of ganglioside ligands for LT-IIb-B exhibiting the most significant increase. No major changes in expression of ganglioside ligands for LT-IIa-B (avidity: GD1b>GM1>GT1b) were detected across either CD8+ T cell or NK cell populations. Taken together these results demonstrate dynamic changes in the patterns of ganglioside expression throughout CD8+ T cell and NK cell differentiation. The unique and shared pattern suggests the existence of cell signaling similarities during development and function of these distinct cell types, and this relationship could prove invaluable in the development of novel cancer immunotherapies. Citation Format: Madison K. Ritter, Mary-Peyton A. Knapp, Taylor A. Johnson, Natalie D. King-Lyons, Lorrie Mandell, Jennifer T. Grier, Terry D. Connell, Sergio Arce. Dynamic changes in patterns of ganglioside expression characterize maturation of cytotoxic T cells and natural killer cells into effector cells and suggest a close relationship between the two cell types [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4525.

Abstract A25: Differentiation of human naive T cells to various effector memory cell subtypes correlates with increased binding of the B subunit of Type-IIb heat-labile enterotoxin (LT-IIb-B5) to its cognate ganglioside receptors

Abstract The initial antigenic activation of T cells involves localization of the T-cell receptor to lipid rafts, of which gangliosides are major components. To understand the role of lipid rafts in the activation and differentiation of CD4+ and CD8+ T cells, it is necessary to dissect the ganglioside composition in each respective T-cell subset. In the present study, we used the B subunits of type-II heat-labile enterotoxins (LT-IIa-B5, LT-IIb-B5 and LT-IIc-B5), which possess defined ganglioside-binding specificities, as molecular probes to dissect the membrane ganglioside composition of human T cell subsets. Peripheral blood mononuclear cells isolated from leukocyte reduction filters by Ficoll density gradient centrifugation were stained with recombinant LT-IIa-B5, LT-IIb-B5, mutant LT-IIb-B5(T13I) or LT-IIc-B5 and with monoclonal antibodies to CD4, CD8, CD27, CD45RA, CD45RO and CD62L followed by flow cytometric analysis. Our results show that ligands for LT-IIa (gangliosides GD1b, GM1, and GT-1b), LT-IIb (gangliosides GD1a, GT1b and GM2), and LT-IIc (gangliosides GM1, GM2, and GM3) are increasingly expressed during differentiation from naïve (CD4+ or CD8+CD45RO-CD27+) to memory (CD4+ or CD8+CD45RO+CD27+) T cells, and that discrete subsets of central memory (CD4+ or CD8+CD45RA-CD62L+), effector memory (CD4+ or CD8+CD45RA-CD62L-), and terminally differentiated effector memory (CD4+ or CD8+CD45RO+CD27-) T cells express the highest ganglioside levels, particularly of LT-IIb-ligands. On the other hand, mutant LT-IIb-B5(T13I), which had negligible binding in vitro to gangliosides GD1a, GT1b, and GM2, exhibited no detectable binding to naive or central memory T cells, but significantly bound subsets of terminally differentiated effector memory (CD4+ and CD8+) T cells. Our results suggest an important role for gangliosides GD1b and GM1 in naive T-cell responses, while central memory, effector memory, and terminally differentiated effector memory T-cell responses may be more dependent upon gangliosides GD1a and GT1b. Furthermore, the lymphocyte-binding activities of LT-IIb-B5(T13I) confirm that its parental B-pentameter essentially recognizes gangliosides GD1a, GT1b, and GM2 on T cells and suggest that LT-IIb-B5 (T13I) may bind to one or more unknown receptor(s) expressed on subsets of terminally differentiated effector memory (CD4+ and CD8+) T cells. Citation Format: Taylor A. Johnson, Madison K. Ritter, Mary-Peyton A. Knapp, Robert O. Rainer, Nathalie D. King-Lyons, Terry D. Connell, Sergio Arce. Differentiation of human naive T cells to various effector memory cell subtypes correlates with increased binding of the B subunit of Type-IIb heat-labile enterotoxin (LT-IIb-B5) to its cognate ganglioside receptors [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A25.

Regulation of triglyceride metabolism in medaka (Oryzias latipes) hepatocytes by Neu3a sialidase.

Fish store triglycerides (TGs) in the liver, muscle, and adipose tissue and TGs constitute an energy source upon metabolic demand. The liver generally plays important roles in lipid metabolism. Recent studies have suggested the possibility of hepatic lipidmetabolic regulation by ganglioside in mammals; however, ganglioside-mediated regulation of lipid metabolism is unclear in fish. This study aimed to clarify the role of ganglioside in fish TG metabolism, with particular reference to Neu3a, a ganglioside-specific sialidase expressed in the fish liver. Under fasting conditions, there was a decrease in hepatic TG contents, and neu3a mRNA level was significantly up-regulated in the medaka liver. To determine the role of Neu3a in hepatic lipid metabolism, Neu3a stable transfectants were generated using fish liver Hepa-T1 cells. After treating Neu3a cells with oleic acid, reduction of TG was detected in comparison with the mock cells. Furthermore, lipase activity was greater in Neu3a cells than in mock cells. To examine which ganglioside regulates these events, alterations of ganglioside composition in Neu3a cells were analyzed. Neu3a cells exhibited increased level of lactosylceramide (LacCer), a Neu3 enzymatic product originating from GM3. In addition, exposure of LacCer toward Hepa-T1 cells resulted in an increase of neutral lipase activity. The present results suggest that Neu3a up-regulation in medaka under fasting condition accelerates hepatic TG degradation for energy production via GM3 desialylation.

Dietary Intake of Gangliosides and Correlation with Serum Ganglioside Concentration: Cross-Sectional Study among Chinese Toddlers Aged 24-48 Months

Gangliosides are a group of sialic-acid-containing sphingolipids, found in brain and neural tissues. The various biological roles of gangliosides have been well reported and include calcium homeostasis, regulation of neurons, neural repair, immune system functions, and cellular functions. Furthermore, dietary gangliosides have been shown to improve cognitive development in the early postnatal period and to increase brain neuroplasticity. However, the dietary intake status of gangliosides among Chinese toddlers is unknown. The aim of this study was to determine the dietary intake and food source of gangliosides among Chinese toddlers and to probe its correlation with serum ganglioside concentration. Total of 213 Chinese toddlers aged 24-48 months were enrolled in this cross-sectional study in Beijing and Xuchang City, China. A food frequency questionnaire and 24-h dietary recall methods were used to collect both long- and short-term dietary information. Food items selected from dietary records and blood serum samples collected from 197 toddlers were analyzed for ganglioside composition using high performance liquid chromatography‒mass spectrometry. The average dietary total ganglioside intake among the Chinese toddlers was 4.21 mg/day. Dairy products, meats, and growing-up milk powders were the predominant food sources of dietary gangliosides with relative proportions of 38, 31, and 29% of the daily dietary total ganglioside intake, respectively. The average serum total ganglioside concentration was 14.86 μg/mL, with GM3 making up 96%. No significant correlation was found between the dietary total ganglioside intake and the serum total ganglioside concentration. As this correlation was inconclusive, further investigation is required to understand ganglioside metabolism and the mechanisms contributing to the role of gangliosides in the growth and cognitive development of toddlers.

Neuronal Signaling by Thy-1 in Nanodomains With Specific Ganglioside Composition: Shall We Open the Door to a New Complexity?

Thy-1 is a small membrane glycoprotein and member of the immunoglobulin superfamily of cell adhesion molecules. It is abundantly expressed in many cell types including neurons and is anchored to the outer membrane leaflet via a glycosyl phosphatidylinositol tail. Thy-1 displays a number of interesting properties such as fast lateral diffusion, which allows it to get in and out of membrane nanodomains with different lipid composition. Thy-1 displays a broad expression in different cell types and plays confirmed roles in cell development, adhesion and differentiation. Here, we explored the functions of Thy-1 in neuronal signaling, initiated by extracellular binding of αVβ3 integrin, may strongly dependent on the lipid content of the cell membrane. Also, we assort literature suggesting the association of Thy-1 with specific components of lipid rafts such as sialic acid containing glycosphingolipids, called gangliosides. Furthermore, we argue that Thy-1 positioning in nanodomains may be influenced by gangliosides. We propose that the traditional conception of Thy-1 localization in rafts should be reconsidered and evaluated in detail based on the potential diversity of neuronal nanodomains.